Vincent M. Eckhart

Vincent M. Eckhart
Grinnell College · Department of Biology

Ph.D.

About

50
Publications
8,607
Reads
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2,540
Citations
Introduction
I am - curious about plant adaptation and distribution; - lucky to get to teach good students; - fortunate to collaborate with smart colleagues; and - reluctantly putting the nerd in social nerdworks.
Additional affiliations
August 1996 - present
Grinnell College
August 1996 - present
Grinnell College
Position
  • Professor (Full)
August 1994 - June 1996
Cornell University
Position
  • Developmental constraints in the evolution of plant mating systems
Education
September 1984 - December 1991
University of Utah
Field of study
  • Biology
August 1980 - May 1984
Pomona College
Field of study
  • Biology

Publications

Publications (50)
Preprint
Full-text available
Bet hedging consists of life history strategies that buffer against environmental variability by trading off immediate and long-term fitness. Delayed germination in annual plants is a classic example of bet hedging, and is often invoked to explain low germination fractions. We examined whether bet hedging explains low and variable germination fract...
Article
Full-text available
Premise: Whether drought-adaptation mechanisms tend to evolve together, evolve independently, or evolve constrained by genetic architecture is incompletely resolved, particularly for water-relations traits besides gas exchange. We addressed this issue in two subspecies of Clarkia xantiana (Onagraceae), California winter annuals that separated appr...
Article
Full-text available
Spatial partitioning is a classic hypothesis to explain plant species coexistence, but evidence linking local environmental variation to spatial sorting, demography, and species’ traits is sparse. If co‐occurring species’ performance is optimized differently along environmental gradients because of trait variation, then spatial variation might faci...
Preprint
Full-text available
Premise Whether mechanisms of drought adaptation tend to evolve together, evolve independently, and/or evolve constrained by genetic architecture is incompletely resolved, particularly for water-relations traits besides gas exchange. We addressed this question in two subspecies of Clarkia xantiana (Onagraceae), California winter annuals that diverg...
Preprint
Full-text available
The immediate capacity for adaptation under current environmental conditions is directly proportional to the additive genetic variance for fitness, VA(W). Mean fitness, W, is predicted to change at the rate (VA(W))/W, according to Fishers Fundamental Theorem of Natural Selection. Despite ample research evaluating degree of local adaptation, direct...
Article
Species’ geographic distributions have already shifted during the Anthropocene. However, we often do not know what aspects of the environment drive range dynamics, much less which traits mediate organisms’ responses to these environmental gradients. Most studies focus on possible climatic limits to species’ distributions and have ignored the role o...
Preprint
Full-text available
Species’ range limits offer powerful opportunities to study environmental factors regulating distributions and probe the limits of adaptation. However, we rarely know what aspects of the environment are actually constraining range expansion, much less which traits are mediating the organisms’ response to these environmental gradients. Though most s...
Article
Full-text available
Whether close evolutionary relatives can coexist is expected to depend on evolutionary divergence in niches relative to divergence in competitive abilities. We investigated how plant species' responses to soil texture might affect coexistence by analysing distributions, seedling emergence and performance, and competitive abilities of the winter ann...
Article
Full-text available
Hutchinson (1957) defined the ecological niche as a hypervolume shaped by the environmental conditions under which a species can “exist indefinitely”. Although several authors further discussed the need to adopt a demographic perspective of the ecological niche theory, very few have investigated the environmental requirements of different component...
Article
Full-text available
Interestingly, relationships between demographic parameters and occurrence probability did not vary substantially across degrees of shade tolerance and regions. Although they were influenced by the uncertainty in the estimation of the demographic parameters, we found that r was generally negatively correlated with P-occ, while N, and for most regio...
Conference Paper
Full-text available
Background / Purpose: Expecting species distribution models (SDMs) to predict demography is a bit like expecting a cat to be able to drive a car. SDMs and cats have some of the right anatomy for these tasks, but they may be missing some critical pieces, and they are not (necessarily) the right size. For example, SDMs might predict demography rath...
Article
Full-text available
Evolutionary adaptation is a key driver of species' range dynamics. Understanding the factors that affect rates of adaptation at range margins is thus crucial for interpreting and predicting changes in species' ranges. The spatial structure of environmental conditions is one of the determinants of whether and how quickly adaptations occur. However,...
Article
Theory predicts that lack of heritable trait variation and/or maladaptive gene flow can promote the formation of species geographical range boundaries even in the absence of barriers to dispersal. Little is known, however, about the patterns and drivers of differentiation across species' ranges and whether they influence boundary formation in the f...
Conference Paper
Full-text available
Background/Question/Methods Whether closely related species can coexist is expected to depend on their evolutionary divergence in niches, relative to their evolutionary divergence in competitive ability. Also critical is the spatial scale at which niche differences appear. Even if close relatives exhibit strongly conserved environmental responses...
Article
Full-text available
Mutualisms are well known to influence individual fitness and the population dynamics of partner species, but little is known about whether they influence species distributions and the location of geographic range limits. Here, we examine the contribution of plant-pollinator interactions to the geographic range limit of the California endemic plant...
Article
Full-text available
At scales from microsites to entire ranges, species’ distributions reflect limited adaptation and/or limited dispersal. To what extent are specific distribution patterns and processes similar across scales? We investigated environmental effects—presumed because of adaptation—and independent spatial effects—presumed because of dispersal—on distribut...
Article
Full-text available
Potential causes of species' geographic distribution limits fall into two broad classes: (1) limited adaptation across spatially variable environments and (2) limited opportunities to colonize unoccupied areas. Combining demographic studies, analyses of demographic responses to environmental variation, and species distribution models, we investigat...
Article
Full-text available
The co-occurrence of several dimensions of resource separation between coexisting consumers strengthens the hypothesis that the separation arose from and/or ameliorates interspecific competition. The two most common pollinators of the California endemic plant Clarkia xantiana ssp. xantiana (Onagraceae), the bees Hesperapis regularis (Mellitidae) an...
Article
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Low precipitation can limit plant distributions. Soil variation might interact with precipitation gradients to define species borders. Analyzing the eastern species border of the California annual Clarkia xantiana ssp. xantiana, we assessed the following: (1) the geography of plant water status, precipitation, and soil; (2) soil control of plant wa...
Article
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The effect of shoot damage on plant performance depends partly on a plant's ability to recover by growth compensation. Plant populations in tallgrass prairie likely experience, or historically experienced, high risks of damage and therefore might be expected to have evolved significant compensation ability. We investigated shoot damage and subseque...
Article
Sexual selection theory predicts that hermaphroditic plants might trade off seed production to attract pollinators. This paper reports a test of this prediction in gynodioecious Phacelia linearis (Hydrophyllaceae), a species in which attractiveness to pollinators increases with corolla diameter. The relationship between corolla diameter and seed pr...
Article
Under many circumstances pollinators are expected to practice positive frequency–dependent foraging in colour-polymorphic plant populations. Theory suggests, however, that competition for floral resources might favor negative frequency–dependent foraging by some pollinator species, possibly contributing to the maintenance of flower colour variation...
Article
Because the range boundary is the locale beyond which a taxon fails to persist, it provides a unique opportunity for studying the limits on adaptive evolution. Adaptive constraints on range expansion are perplexing in view of widespread ecotypic differentiation by habitat and region within a species' range (regional adaptation) and rapid evolutiona...
Article
Abstract Because the range boundary is the locale beyond which a taxon fails to persist, it provides a unique opportunity for studying the limits on adaptive evolution. Adaptive constraints on range expansion are perplexing in view of widespread ecotypic differentiation by habitat and region within a species' range (regional adaptation) and rapid e...
Article
Both genetic differentiation and phenotypic plasticity might be expected to affect the location of geographic range limits. Co-gradient variation (CoGV), plasticity that is congruent with genetic differentiation, may enhance performance at range margins, whereas its opposite, counter-gradient variation (CnGV) may hinder performance. Here we report...
Article
Full-text available
The reproductive assurance hypothesis posits that selection favors self-pollination in flowering plants where mates and/or pollinators are scarce. A corollary is that self-pollinating populations are expected to be superior colonizers of mate- and pollinator-scarce environments. The California annual Clarkia xantiana includes outcrossing population...
Article
Darwin’s theory of natural selection successfully explains why organisms are designed to meet environmental challenges, his simple proposal being that heritable traits that confer survival benefits on individuals will come to predominate in populations (Darwin 1859). Thus, it was a special challenge for him to explain the evolution of secondary sex...
Article
Full-text available
Allocation trade-offs should be measured as opportunity costs, estimating what individuals sacrifice in one function by allocating to others. We investigated opportunity costs of male function in gynodioecious Phacelia linearis, asking whether nutrient limitation contributes to them. This hypothesis predicts that hermaphrodites experience greater n...
Article
Full-text available
The common sexual systems in seed plants are hermaphroditism, dioecy, and gynodioecy. Here we attempt to explain this pattern by extending the `classical' resource allocation model for the evolution of sexual systems. First we derive the equilibrium frequencies of all sex morphs and the sex allocations of hermaphrodites as functions of the male and...
Article
Reports on gynodioecy in Phacelia linearis, an insect-pollinated annual plant in which gender inheritance appears to be nuclear. Twenty-six populations surveyed in N Utah contain a majority of perfect-flowered hermaphrodites, but most (22) also contain male-sterile individuals (females), at frequencies of up to 0.16. The hermaphrodite selfing rate...
Article
Gynodioecy is a dimorphic breeding system in which hermaphrodite and female individuals coexist in populations. Theoretical models have shown that if nuclear genes control sex expression, then gynodioecy can evolve only when females have large advantages in one or more fitness components. These female advantages must be large enough that females' e...
Article
Full-text available
Variation in pollinator assemblages at several levels can affect the likelihood of evolutionary specialization of plants for particular pollinators and patterns of natural selection on floral characters. This paper describes variation in a pollinator assemblage (mainly solitary bees) at three levels - geographic occurrence, abundance, and foraging...
Article
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The evolution of gynodioecy depends in part on the location (nucleus or cytoplasm) of gender-determining genes. Characters genetically correlated with gender also can be important in the evolution of this sexual system. For example, gender differences in the costs of flowers affect the potential for resource compensation by females for the loss of...
Article
The evolution of gynodioecy depends in part on the location (nucleus or cytoplasm) of gender-determining genes. Characters genetically correlated with gender also can be important in the evolution of this sexual system. For example, gender differences in the costs of flowers affect the potential for resource compensation by females for the loss of...
Article
Full-text available
Summary Individual plants in gynodioecious populations ofPhacelia linearis (Hydrophyllaceae) vary in flower gender, flower size, and flower number. This paper reports the effects of variation in floral display on the visitation behaviour of this species' pollinators (mainly pollen-collecting solitary bees) in several natural and three experimental...
Article
Full-text available
Several recent studies have shown that males and females in some populations of dioecious plants are spatially segregated with respect to an environmental gradient. The inference is often made that such spatial segregation of the sexes (SSS) is favoured by selection because it reduces competition between individuals of opposite sex (sexual "niche p...

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